Christopher M. Danforth and Peter Sheridan Dodds, statisticians at the University of Vermont, analyzed song lyrics, blog posts, and speeches for certain emotional keywords in order to discern the collective moods of the American people over time:

Still, the University of Vermont study presents what could be a complementary measure, and it provides a few decent cocktail-party nuggets along the way. Dr. Dodds and Dr. Danforth downloaded the lyrics to 232,574 songs by 20,025 artists released between 1960 and 2007, from the Web site hotlyrics.net. From another site, wefeelfine.org, they pulled more than nine million sentences that used some form of the verb feel — as in “I feel relieved” — from 2.3 million blogs from 2005 to 2009. They also analyzed State of the Union speeches going back to George Washington’s. They then rated the psychological charge, or “valence,” of a significant subset of the words on a 10-point scale: from triumphant (8.82) and love (8.72) down to disgusted (2.45) and suicide (1.25).

Some of the findings were expected. Sept. 11, 2001, was rock bottom, for instance. Others were less so: the day that Michael Jackson died also lowered people’s mood significantly. The high-water mark was the day President Obama was elected, when the word “proud” was predominant.

Christmas and Valentine’s Day regularly popped as positive times, although words like “guilty” were associated with Christmas and “waste” and “lonely” with Valentine’s Day.